1. Field of the Invention
This invention is directed to an interface between a flexible shaft and a circuit interrupting device, and more particularly to such an interface between a linearly movable rod of the flexible shaft and a handle of a circuit breaker.
2. Background of Information
Circuit interrupters (e.g., circuit switching devices, circuit breakers, etc.) are generally old and well-known in the art. Examples of circuit breakers are disclosed in U.S. Pat. Nos. 4,489,295; 4,638,277; 4,656,444 and 4,679,018. Such circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload and relatively high level short circuit condition. Molded case circuit breakers include at least one pair of separable contacts which may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to an overcurrent condition. A common type of circuit switching device has a front face with a manual handle which may be arcuately operated between an on position and an off position. A common type of circuit breaker has a similar handle which is connected to movable contacts through a spring powered, over center toggle device which trips the contacts open and moves the handle to an intermediate trip position in response to certain overcurrent conditions. A fourth, reset position, which is beyond the off position and opposite from the on position, is used to reset a trip mechanism of the circuit breaker following a trip condition.
For a variety of reasons, such as operator safety, circuit interrupters are commonly mounted behind a panel or behind a door in a cabinet. Typically in these installations, the handles of the circuit interrupters are not directly accessible by the operator. In some of these installations, a remote handle mechanism is mounted to the opposite side of the panel or door and a mechanical linkage is used to interconnect the remote handle mechanism with the circuit interrupter handle.
In other installations, a flexible shaft replaces the mechanical linkage. The flexible shaft includes a fixed outer jacket having a linearly movable core; a bulkhead hub for securing the fixed outer jacket on one side of the bulkhead and for providing a swivel sleeve on the other side; and a linearly movable rod, which exits an end of the sleeve opposite from the bulkhead and which is attached to the movable core within the sleeve. In such other installations, the remote handle mechanism drives one end of the core of the flexible shaft in a linear push-pull manner. The rod at the other end of the flexible shaft is used to drive a sliding operating mechanism in a similar linear push-pull fashion. The sliding operating mechanism is mounted on the front face of the circuit interrupter and has a hole for inserting the circuit interrupter handle therethrough. In turn, the linear motion of the sliding operating mechanism is used to simulate the arcuate motion of the circuit interrupter handle.
Operability of the remote handle mechanism with the flexible shaft and the sliding operating mechanism is limited in several ways. First, friction between the sliding operating mechanism and the circuit interrupter handle increases the operating forces required to drive the flexible shaft. Second, the force applied by the sliding operating mechanism to the circuit interrupter handle is generally angled away from a tangent to the arcuate rotation path of the handle. Thus, only a fraction of the force provided by the flexible shaft is applied to rotate the handle. Finally, because the hole of the sliding operating mechanism generally drives the handle at a point below an end of the handle, only a fraction of the available handle leverage is utilized. Therefore, an additional force, beyond the operating force at the handle end, is required.
There is a need, therefore, for a flexible shaft interface for a circuit interrupter handle that significantly improves operability and reduces the operating force required to drive the flexible shaft.
There is a more particular need for such an interface that reduces friction between the interface and the handle.
There is another more particular need for such an interface that increases leverage between the interface and the handle.
There is an additional need for a flexible shaft interface for a circuit interrupter handle that significantly reduces the operating force required to drive the flexible shaft.
There is yet another need for a flexible shaft interface for a circuit interrupter handle that cooperates with the handle without requiring a modification of the handle.